Unsatisfactory outcomes following unicompartmental knee replacement for partial thickness cartilage loss: a medium-term follow-up

Journal article

Purpose

Whilst medial UKR is indicated for full-thickness cartilage loss (FTCL) on occasion it has been used to treat partial-thickness cartilage loss (PTCL). This matched case-control study investigates the five-year outcomes in a consecutive series of UKR implanted for PTCL.

Methods

Between 2002 and 2014, 94consecutive UKR (90patients) were implanted by two surgeons for PTCL and followed up independently for a mean 6years (range 1-13). These cases were matched 1:2 based on age, gender and preoperative OKS with knees with FTCL anteromedial osteoarthritis managed with UKR. Functional outcomes, implant survival and incidence of reoperations was assessed at one, two and five years. A sub-study of 36knees (36patients) with PTCL who had had pre-operative MRI was performed to identify whether there were any MRI factors that predicted outcomes.

Results

Knees with PTCL had significantly worse functional outcomes (OKS and AKSS-O) at one, two and five years postoperatively. A quarter of knees with PTCL reported fair or poor results and a fifth failed to achieve a clinically significant improvement from baseline of four points or more on the OKS, double that seen in knees with FTCL. Whilst no difference in implant survival was detected between groups, knees with PTCL had a triple the reoperation rate with the majority, three-quarters, being arthroscopies for persistent pain.

Patients with PTCL who achieved fair or poor outcomes were younger with worse preoperative functional scores, compared to those who achieve good or excellent outcomes however no other differences in baseline demographics were seen. MRI findings (FTCL, subchondral oedema, synovitis or effusion) did not provide additional prognostic information.

Conclusion

Medial UKR should be reserved for patients with FTCL, whilst some patients with PTCL do achieve good results, at present, we cannot identify which these will be and in this situation MRI is not only unhelpful but also misleading.

Authors: Hamilton, T; Pandit, H; Inabathula, A; Ostlere, S; Jenkins, C

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: British Editorial Society of Bone and Joint Surgery
• Journal: Bone and Joint Journal
• Volume: 99-B
• Issue: 4
• Pages: 475-482
• Publication date: 2017-04-01
• Acceptance date: 2016-12-07
• DOI: 10.1302/0301-620X.99B4.BJJ-2016-1061.R1
• EISSN: 2049-4408
• ISSN: 2049-4394
• Keywords: partial thickness cartilage loss; unicompartmental knee replacement; functional outcome; implant survival; patient selection